Locking File for copy

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I have a small script that works where it copies a file from one Windows server to another. The destination file is always overwritten. Now I think I should check if the file I am copying from (sourceFile) is opened by someone and also check if the file I am copying to (destinationFile) is being open or being used. Here is my current copy command:

Use File::Copy
...
copy($a,$b) ||  die "$!";
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Please advise how I can do this because I am not sure about opening it up and how flock works?

open(INPUT, "<$a");  
@data = <INPUT>;        
close(INPUT);            
open (OUTPUT, ">$a"); 
flock(OUTPUT, 2);        
copy($a,$b) ||  die "$!";
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Re: Locking File for copy by McDarren (Abbot) on Aug 02, 2006 at 02:00 UTC
One thing you should be aware of, and keep in mind, is that file locking in Perl is advisory only. That is, even if you open a file in locking mode, there is nothing to stop some other script or process from clobbering the file if it isn't observing file locking. Programming Perl (aka - The Camel, 3rd Edition) has a very good discussion on File Locking in Chapter 16 (beginning on page 419), with plenty of examples. If you have a copy, then I'd thoroughly recommend reviewing this. Failing that, there is always the flock documentation, as well as some discussion on file locking in the DB_File documentation. Hope this helps, Darren	[reply]
Re: Locking File for copy by duff (Parson) on Aug 02, 2006 at 03:21 UTC
I think you want to use Win32::File to set the file you're reading as read only. Check the rest of the Win32 namespace for how to check the other file. I'm sure there's a module for you in there (caveat emptor, I am not a Windows user if I can help it). duff	[reply]